The present invention relates to the field of data and/or power transmission. More specifically, it relates to the field of apparatus for transmitting data and/or power through such downhole tool strings.
Downhole tool strings, such as drill strings, injecting strings, and production strings, have become increasingly versatile in the last half century. In addition to traditional oil, gas, and geothermic exploration and production purposes, tubular tool strings are often used for what is known as horizontal directional drilling to install underground power lines, communication lines, water lines, sewer lines, and gas lines. This sort of downhole drilling is particularly useful for boring underneath roadways, waterways, populated areas, and environmentally protected areas.
The increased versatility of downhole drilling with tool strings has led to a higher demand for apparatus that are able to transmit a power signal to downhole equipment as well as transmit data between downhole and surface tools. Hence, several different approaches to solving the problem of transmitting an electrical signal across the joints of a tool string have been developed and are known in the art.
U.S. Pat. Nos. 6,670,880; and 6,717,501 to Hall, both of which are incorporated herein by reference for all that they disclose, teach of a system wherein tubular components are coupled at threaded joints and comprises a signal transmission system in the tool string. Other downhole telemetry systems are disclosed in U.S. Pat. No. 6,688,396 to Floerke et al and U.S. Pat. No. 6,641,434 to Boyle et al, which are also herein incorporated by reference for all that they contain.
Optimally, a system for transmitting power or data between surface equipment and downhole tools in a tool string should be transparent to the tool string operator or crew, as time delays introduced by a complicated telemetry system may represent a significant amount of money.